ref: b88dac8938106537460889e5eacaaafe59715048
parent: de3097aa2373a441b76364cc9a813b29462f86a1
author: hkuang <hkuang@google.com>
date: Mon Mar 16 12:17:51 EDT 2015
Safely free all the frame buffers after all the workers finish the work. Issue: 978 Change-Id: Ia7aa809095008f6819a44d7ecb0329def79b1117